1. Field of the Invention
This invention relates to the field of tools and more particularly to the field of specialized tools for maintaining transmission lines carrying volatile fluids under pressure.
2. The Prior Art
Here incorporated by reference is the prior patent specification entitled "Element Removal Tool For System Carrying Fluid Under Pressure" Ser. No. 06/565 636, filed Dec. 27, 1983. Described in that specification is a tool for replacing flow sensing elements, such as axle boxes, in transmission lines carrying fluid under pressure. The described tool includes a base sealing portion, a detachable stuffing box portion and an interposed gate valve. The tool also includes an element removal portion having a shaft and an attached socket adapted to engage the element to be replaced.
In using the described tool for element replacement, the shaft is first employed to extend the socket out past the base at which point the socket is engaged onto a defective element in a given transmission line. The composite tool is then brought down around the element and secured on the transmission line, thus creating a sealed chamber around the shaft and socket assembly and over the subject element. By means of the shaft and socket, the defective element is then disconnected from the transmission line. The shaft is then used to withdraw the socket and its engaged element into the stuffing box, after which the gate valve is closed. With the valve closed, the stuffing box may be detached from the base sealing portion without a depressurization of the transmission line. The detachment of the stuffing box exposes the withdrawn socket, thus enabling the engaged element to be removed from the socket.
For element replacement, the reverse process begins with a new element being inserted into the socket. The stuffing box is then reattached to the base sealing portion, the gate valve opened and the shaft employed to slide the socket and new element back into contact with the transmission line. After the element is then re-inserted, the socket is disengaged and the overall tool removed from the pressurized line.
As more fully discussed in the incorporated specification, the subject tool represents a significant advance over previous replacement techniques in that whereas replacement previously required several hours of labor by several people under conditions involving a degree of physical danger, replacements using the new tool may now be accomplished with greater safety by a single operator in approximately 15 minutes.
Despite the significant advantages of the new tool, however, several difficulties have been encountered. These difficulties have been especially apparent in the typical operational environment where the element being replaced is the axle box of the gas flow meter. As will be further discussed below, such axle boxes include an indexing axle having an end portion denominated the "tail" which extends into the meter's gas flow chamber and which is adapted to be received into a companion mating receptacle in the meter's paddle-like activator portion, denominated the "undergear." During ordinary conditions where gas flow is sufficient to cause the activator paddle to rotate at some significant rate, the respective structures are configured such that the mating of the axle tail with the undergear receptacle is basically self-seating. When the gas flow is sufficient, therefore, proper indexing operation of a replacement axle box assembly may be achieved simply by bringing the new axle box into contact with the undergear. It has now been discovered, however, that where the gas flow is rather minimal, the undergear paddle, if still rotating at all, can slow to a rotation rate insufficient to induce the desired self-seating. Under these alternative conditions, therefore, the tail must be affirmatively brought into co-alignment with the undergear mating receptacle in order for seating to take place. For the tool in its existing form, the required co-alignment could be achieved only by resorting to various makeshift alignment practices of a clearly dissatisfying nature.
In addition, because the tool in general and the base sealing portion in particular is typically constructed of a solid metal material, the insertion of the replacement axle box into its associated mounting receptacle in the transmission line has been a "groping in the dark" type operation, further complicated by both the now discovered additional necessity of waiting until the overall tool is disconnected from the transmission line before being able to determine whether the indexing axle is properly engaged by virtue of the axle tail having been properly seated in its associated undergear receptacle.
It is accordingly a first object of the present invention to overcome the disadvantages of the prior art.
It is another object of the present invention to provide for the subject tools the capability of affirmatively aligning the tail of an indexing axle with an undergear mating receptacle during element replacement operations.
It is a further object of the present invention to provide for the subject tools the capability of monitoring the progress of replacement operations without having to remove an engaged tool from a subject transmission line.